YITH WooCommerce Cart Messages allows you to create custom messages that will be displayed in one or more pages of the website (Product page, Archive page, Cart, and Checkout page). Messages can be displayed at all times or only for specific products in the cart.
Thanks to this integration, each custom message you have created can be shown in the popup when a product is added to the cart.
After installing and activating both plugins, you can create your custom messages from YITH > Cart Messages > Add new message. All the way on the bottom, you will find the option Show on “Added to Cart” popup, if enabled, you can show the message inside the popup that will open after adding the product to the cart.